A compound of formula I: ** Formula ** or a pharmaceutically acceptable derivative thereof, wherein X is O, S, N-CN, N-OH or N-OR10； W is N or C； the broken line represents the presence or absence of a link, and when the broken line represents the presence of a link or W is N, then R4 is absent, otherwise R4 is -H, -OH, -OCF3, -halo, -alkyl (C1- C6), -CH2OH, -CH2Cl, -CH2Br, -CH2I, -CH2F, -CH (halo) 2, -CF3, -OR10, -SR10, -COOH, -COOR10, -C (O) R10, -C (O) H, - OC (O) R10, -OC (O) NHR10, -NHC (O) R13, -CON (R13) 2, -S (O) 2R10 or -NO2； R10 is alkyl - (C1-C4)； each R13 is independently -H, -C1-C4-alkyl, -C1-C4-alkenyl, -C1-C4-alkynyl or -phenyl； Ar1 is ** Formula ** Ar2 is ** Formula ** c is the integer 0, 1 or 2； Y1, Y2, Y3 are independently C, N or O； where no more than one of Y1, Y2 or Y3 can be O, and for each Y1, Y2 and Y3 that is N, the N is linked to a group R21, and for every Y1, Y2 and Y3 that is C, the C is linked to two R20 groups, with the proviso that there are no more than a total of two (C1-C6) alkyl groups substituted in each of Y1, Y2 and Y3； R12a and R12b are independently -H or -C1-C6 alkyl； E is>； = O,>； = S,>； = CHalkyl (C1-C5),>； = CHalkenyl (C1-C5), -NHalkyl (C1-C6) or>； = N-OR20； R1 is -H, -halo, -C1-C4 alkyl, -NO2, -CN, -OH, -OCH3, -NH2, -C (halo) 3, -CH (halo) 2, -CH2 (halo) , -OC (halo) 3, -OCH (halo) 2 or -OCH2 (halo)； Each R2 is independently: (a) -halo, -OH, -O (C1-C4) alkyl, -CN, -NO2, -NH2, -C1-C10 alkyl, -C2-C10 alkenyl, -alkynyl ( C2-C10), -phenyl, or (b) a group of formula Q； wherein Q is ** Formula ** each Z3 is independently -H, -C1-C6 alkyl, -C2-C6 alkenyl, -C2-C6 alkynyl or -phenyl； J is -OR20, -SR20, -N (R20) 2 or -CN； with the proviso that at least one group R2 is a group of formula Q； each R3 is independently: (a) -H, (C1-C6) alkyl or CH2OR7； or (b) two R3 groups together form a bridge (C2-C6), which is unsubstituted or substituted with 1, 2 or 3 independently selected R8 groups, and whose bridge optionally contains
